1. Field of the Invention
The present invention relates to annuloplasty rings for use in the surgical correction of heart valve disorders. More particularly, the invention relates to annuloplasty rings having the capability to induce healing and/or regeneration of heart valve annular tissue.
2. Description of Related Art
Annuloplasty rings are used by surgeons to repair diseased or damaged heart valves when the disease or damage to the heart valve does not require completely replacing the natural heart valve with a heart valve prosthesis. This therapy is useful when, for example, a disease process has caused the heart valve annulus to dilate (enlarge), thereby preventing the heart valve leaflets from coapting (i.e., contacting one another) to seal against backflow of the blood through the valve.
Annuloplasty rings generally comprise a rigid or flexible ring which is sewn or stapled to the annulus of the heart valve, thereby reducing the diameter of the heart valve annulus to allow the leaflets to coapt and function properly. Since the annuloplasty technique was first implemented, several designs of annuloplasty rings or prostheses have been developed. In one of the earliest designs, a rigid ring was sewn about the valve annulus, see e.g., U.S. Pat. No. 3,656,185 (Carpentier). Other annuloplasty ring designs incorporate fully flexible rings, see e.g., U.S. Pat. No. 5,306,296 (Wright, et al.). Additional annuloplasty ring designs include various partially rigid rings and rings with rigid and flexible portions, see e.g., U.S. Pat. No. 5,061,277 (Carpentier, et al.). Most currently available annuloplasty rings are made of biocompatible fabric, such as polyester, or are a combination of materials such as a rigid core of titanium, polyethylene or silicone and a fabric cover.
A primary limitation of current therapies employing conventional annuloplasty rings or prostheses is the complete absence of any actual healing response for the heart valve tissue. Because there is no healing response, the damage to the valve is not reversed. Thus, continuation of the disease process could lead to the necessity of completely replacing the valve, with ensuing complications to the patient. Thus, surgeons may be performing complete valve replacements under current surgical protocols when valve annuloplasty alone could suffice if a healing response in the heart valve tissue could be initiated.
U.S. Pat. No. 6,024,918 (Hendriks, et al.) describes a method of making a medical device having a biomolecule immobilized on a substrate surface. Annuloplasty rings are suggested among a number of devices that could potentially be modified by attachment of a biomolecule, however no such device is specifically exemplified.
Published PCT application WO 97/16135 (Tweden et al.) discloses a fully bioresorbable annuloplasty prosthesis made of a bioresorbable polymer. Because that prosthesis, which may also include a growth factor, is completely resorbable, it is intended to be replaced by tissue over time once it is attached around a native heart valve annulus. Successful therapy using an annuloplasty ring made of completely bioresorbable material relies on an ideal scenario in which a complete healing and/or restoration of annulus competency is effected before the physical support provided to the annulus by the prosthesis is lost due to degradation. However, even determining of the ultimate degree of any healing response with any growth factor or growth factor mixture, much less accurately predicting the speed of such response, is impossible given current knowledge. One drawback of annuloplasty therapies using this kind of prosthesis in real world therapeutic applications is that resorption of the ring is can result in re-dilation of the annulus if the healing response is less than complete.
The present invention seeks to overcome these and other drawbacks inherent in the prior art by providing methods and devices for promoting actual repair and/or regeneration of diseased or damaged heart valve annulus tissue in current annuloplasty ring therapies while maintaining all of the benefits of existing valve annuloplasty therapies that employ non-resorbable rings.
Accordingly, in one embodiment, the present invention provides a non-resorbable annuloplasty ring incorporating a growth factor for regeneration of heart valve annulus tissue. In one embodiment, the invention comprises a flexible annuloplasty ring comprising an outer covering of polymeric cloth. In another embodiment, the invention comprises a rigid annuloplasty ring.
In a further embodiment, the invention comprises a non-resorbable annuloplasty ring incorporating a mixture of growth factors for regeneration of heart valve annulus tissue while providing all the benefits of existing annuloplasty ring therapy. The annuloplasty ring may comprise a rigid or flexible ring, and may incorporate an inner polymeric member.
In yet another embodiment, the invention comprises a non-resorbable annuloplasty ring comprising a first growth factor reservoir for rapid release into the heart valve tissue and a second growth factor reservoir for relatively slower release into the heart valve tissue. The first growth factor reservoir may comprise a cloth outer covering of the annuloplasty ring or an inner fabric or foam member. The second growth factor reservoir may comprise a degradable or resorbable polymer containing a growth factor.
In another embodiment, the invention comprises a non-resorbable annuloplasty ring comprising a flexible annuloplasty ring having a cloth covering comprising a growth factor mixture and a resorbable polymeric inner member comprising a growth factor mixture, the growth factor mixtures being capable of effecting a healing response in damaged valve annulus tissue. These and other embodiments, features and advantages of the present invention will become apparent with reference to the following description.